Electric furnace.



H. P. D. SGHWAHNE ELECTRIC FURNACE.

APPLIOATIUFX FILED SEPT. 26. 1912.

steamed July 28, 1914.

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Patented July 28, 1914.

' Application filed September 26, 1912. Serial No. 722,46 l.

To all whom it may concem Be it known thatl, Hummer: F. D, SCHVVAHN, a citizen of the United States, and resident of the city of Belleville, in'the county of StfClair and State of Illinois, have invented anew and useful Improvement in Electric Furnaces, of which the'following is a full, clear, and exact description,

reference being had to the accompanying drawings, forming part of this invention.

My invention relates to the reduction of metal bearing materials such as skimmings, scruif and dresses from remelting and casting metals any description and the refining of brass turnings and other metal scraps, but also ores or compounds especially those with an aluminum content may be treated and reduced by this method -which is designed tovprovide a process which will practically avoid the loss of any metal and work rapidly and cheaply. And furthermore relates to apparatus particularly adapted for and designed to accomplish the above in a practical, effective and commercial manner.

Essentially my invention consists in sub- 1 jecting metal bearing materials in presence of a reducmg agent 111 some form, gases 1ncluded, to the radiant heat from a resister within an electric circuit and permitting the resultant fused mass'to pass through. said resister to be subjected thereby to higher heats in a reducing atmosphere and complete the reduction and refining of their metal content. 9

In carrying out my method I employ a substantially closed electric furnace which is of the resistance type, and consists essentially, taking the smallest size of a furnace for an example, of two electrodes, spaced from each other, and an intermediate resistance body of a carbonaceous composition in which the heat is generated, and through which the resultant fused mass from the ma terial under treatment is permitted to pass, anduse in conjunction therewith some form of a reducing agent preferably carbonaceous materials such as for instance hydrocarbons, which will unite with the oxygen of the oXids in the material under treatment and that of the air'present in the furnace and ance body of carbonaceous material is charged metal baa-ring materials. under treatment, while I employ in the lower-portion ofthe furnace a substantially closed crucible or well, into which the reduced or fused metal descends with the slag, ifany, and enabling it to collect. in a reducing'atmosphere, thus protecting it from oxidation, and the metal may be tapped out directly from the well through a taphole or from condensers in case some of the metal, such as sodium orzinc, has been volatilized and recovered in said condensers. I also employ some refractory checkers upon which the carbonaceous resistance body is spread to relieve automatically and continuously said resistance body from the fused material passing into and through the same thereby preventing a bridging over the resister' by the reduced metal, and through which this electric current would pass between the electrodes without affecting the resister, and therefore would make the processinoperative for a continuous operation. And on the other hand these checkers permit or 'accel- 'erate the evolving of the naturally, or purposely made, volatile constituents of the charge by certain fluxes, as known to those skilled in the art, for their separate recovery from the non-volatile metals and slag. if any, and which may suflioe if. the material under treatment is of'an electrically resisting nature, such as for instance oxids' mixed with carbon, drosses, sulfate of aluminum or ores, but in case pf treating a very conduc-v tive material such as aluminum or brass turnings, zinc or; tin skimmings from galvanizing or tinning I use a layer of said refractory checkers also above; said carbonaceous resistance body so that said metals can not'comein direct contact with the same before their fusing by its radiating heat,

which occurs gradually with the reduction also exceedingly operative for such last named materials.

An example or embodiment of my invention is shown in-the accompanying drawings in which, Figure 1, isa vertical right-left middle section; Fig. 2, ave rtical front-back middle section; and Fig. 3-, a horizontal cross section taken on line AA of Fig. 1.

Like numbers refer to like parts throughout the drawing.

1 are a number of arches dividing the furnace shaft into' the upper chamber or furnace 2 and lower chamber or Well 3, and these arches 1 leaving spaces or canals between each other indicated byway and are suitably constructed of refractory material such as for instance magncsite or chromebrick with which also the entire furnace is suitably lined within. A taphole 5 is provided on the bottom and another tappinghole 6 above the first but below the exits 7 into the condensers 8. And said. condensers are provided for the recovery of any volatile metal or metallic compound separated from the fused metal bearing material in passing through the resistance body of carbon fragments or parts and refractory checkers.

9 and 10 represent carbon electrodes both extending through the adjustable boxes 11 and 12 respectively, into the furnace 2 in about the form as shown. 9 and 10 are surrounded by broken carbon 13 of some form. Crushed'foundry coke passing over a 0.25-inch (6 min.) ring and through a 0.5-inch (12 mm.) ring will protect said electrodes 9 and 10 and make a good contact between the same and the resistance body if suitably consisting of calcined oil coke, in case of reducing or remelting aluminum, or of foundry coke. for the reduction and treatment of other metals. And I use either of them crushed to pass over a 0.5-inch (12 mm.) ring and through a 0.75-inch (18 mm.) ring. And this coke, which is porous, I preferably wash or permeate with slaked lime or other suitable alkaline earth-metal salts to fill its pores,.

whereby not only the resistance to an electric current is promoted but also the deposition of metal within the coke is prevented, and the life of the resistance body increased giving-thereby the most satisfactory and uniform results. Although the resistance body 14 can be placed'directly upon the false bottom 1 as its principal sustainer above the well 3, I prefer to place between said arches 1 and resistance body 14 a layer of checkers 15 preferably in form of round balls in size of about 2-1- inches diameter, and suitably composed of magnesite or chrome-brick material. These checkers 15 offer a multitude of surfaces and spaces between the false bottom 1 and resistance body 14:, leading into the canals 4 which discharge into Well 3, while the same kind of checkers above the resistance body, indicated by 1.6 are employed only in remelt-ing' of metals, etc., as above specified, and may be removed if thefurnace is used for the reduction of metals from their ores or compounds which .in themselves form resisters.

1.7 is a hopper for the charging of the material from above, and 18 is a door pro- .its contents desired. rind refractory covering of said heater, while 21 I Said electrodesof the well 3, and consists carbon electrodes Ql'and body suitably consisting of (i-us i, cal-a. passing; over 0.25-inch ((3 mm rine; and through 0.3T-inch (9 mm.) in which the heat is enerated to heat said well 27 and indicates 21 represents alayer of a poor conductor for heat below the heater Q0.

F or a convenient charging; of reducing: and fluxing gases I have provided the pipes 25 and 20; and for the discharging-of the p spent gases from under the roof of the furnace the pipes 27 and are provided. -ind indicates the charged material. under treatment.

For a 50-kilo-watt furnace with one pair of electrodes, as (shown, the distance between the electrode. should be about 36 inches, and the cross-sectional area about lOinches. To maintain an electrical input of 50 kw. a voltage of about 220 volts is required. The

resistance body as it approaches the electrodes 9 and 10 by means of the brokei'i carbon 13 has a very increased cross-section, as to provide a better contact between. the

electrodes 9 and 10 and the resistance body A l-l. the point of Contact with the electro preventsthe dissipation of heat through rc- And this prevents undue heating at les and instance to the passage of the current except at that part of the resistance bcdy'ie: directly under the metal bearingmaterials under treatment. Thus in a way these increased cross-sections perform the mission of electrodes, as they conduct the current from the electrodes proper which are located in a protected part of. the furnace or boxes liand 12, to the part where the transformation into heat is desied, and they do this without any considerable heat being generated in these portions themselves. The temperatures that may be obtained are limited solely by the electrical input and the temperatures allowable by the refractory linings and checkers of the furnace. The available temperatures under ordinary condition are 'irobably not less than 2000 C. he resistance material, of course, reaches a much higher ten'iperaturc, hence, the efficiency of this method in the reduction of aluminum from its OXiCl or compounds, and the reduction and refining of other metals.

In operating the process in the preferred form the resister 14: is first started, suitably by bridging it over with some of the more no i I conductive material 13, as will be understood by those skilled in the art, and switching the current into the resister through the electf odes 9 and 10, when the same soon will become incandescent throughout and is ready then for operation. Meantime the heater 20 heats up the well 3, and then the metal bearing materials may be charged directly upon the resistance body 14, if-the same are or may become resistance conductors on heating, and if not-namely,- they are to remain good. conductors for electricity-then a layer of checkers 16 is first laid over the resistance body 14: so that said checkers come between the charge and said resistance body, as shown in Figs. 1 and 2,

and then such material may be fed, but in that event carbon in some form, gases included, may be charged into the furnace to maintain a reducing atmosphere therein. The resultant fused mass from above the resister passes then over and through the carbonaceous composition and refractory checkers and completes the reduction and refining of the metal bearing material under treatment, which descends then through the canals 4- into the. well 3 from where the metal and slag, if any, may be tapped from time to time, likewise the recovered volatile metals, if any, from the condensers. Successive charges of metal bearing materials mixed with carbon and fluxes, or reducing gases, provided such additions are necessary, may be fed in from time to time, or the charging and discharging may be carried on continuously. v

The replacing of the resistance body 14 and the replenishing of the broken carbon 13 from time to time are'the only items that may be classed as renewals. The metal hearing material being treated is maintained in a reducing atmosphere, the high temperatures of the carbon contact mass 13 near the resistance body 14 giving off a gas of a reducing nature which therefore can be used alone for the maintaining of a reducing atmosphere within the furnace, if desired.

The electric furnace'as herein described is merely the container of the resister, but as a whole is a furnace of the resistance type by which actually the highest temperatures are available, and which varies only with the size of the furnace, and consequently with the enlarging of the furnace also the resistor should be increased in size in its cross-sec tional area and number of electrodes correspondingly for the necessary increased input of electrical currents if the highest efliciency of a larger furnace. isdesired.

Other styles of furnaces as containers for the, resistance body may be employed by me, and bther arrangements made for the combination of the resister 1a and heater 20, and the replenishing ofthe resister may be also accomplished from the carbon present in the charged material under treatment and therefore is used then in the proper size as above specified. Many other changes may be made in the mechanical arrangement which forms a part of the process itself, without departing my from invention.

The advantages of my invention result from the use of the resister or resistance body of carbonaceous material in combination with refractory checkers through which the fused metal bearing material under treatment has to pass for its final reduction and refinin The operation is continuous and rapid and the cost of the furnace and its operation is small.

I claim 1. In an electric smelting and refining furnace of the character herein described, the. combination of two chambers, an upper chamber provided with a resistor over chockers upon a false bottom dividing the furnace into said. two chambers, and checkers adjacent to and above said resister.

2. In an electric smelting and refining furnace of the character herein described, the combination of two chambers, an upper chamber provided with a resister and checkers, and a lower chamber or well with a se- ,ries of condensers attached thereto, and

means for heating the well, as and for the purpose described,

. 3. in an electric smelting and refining furnace of the character herein described, the combination of checkers and a. resister with the resister-bed, the resistor consisting of carbonaceous materials in contact with carbon electrodes; and means for charging and recharging or maintaining of'the resister, and means for relieving said resister of the reduced and refined metal automatically, and means for the charging of the aw materials and reducing gases, and me for the discharging of the resultant aroduct and spent gases, substantially as described.

4. In an electric smeltingand refining furnace of the character herein described, the combination therein of two chambers resultant from a horizontally placed false bottom between the walls of the furnace, and upon which a carbon rcsister in combination with refractory checkers is so arranged as to permit the passage of the reducing gases and of the reduced non-volatileand volatile metals formed in the resistor into the chamber or well beneath the false bottom, and means for heating the well, and a series of condensers attached to the well, as and for the purpose specified.

5. In an electric smelting and refining furnace of the character herein described, the combination therein of two chambers resultant from a false bottom placed between the walls of the furnace and upon which a carbon resistor. in combination with refractory checkers is so arranged as to prevent the direct contact of the unfused charge with said. resister but ermit the passage of the reducing and 'fluxlng gases, and of the fused nondmlatile and volatile -meta1s 5 through said Iesister mm the chamber 01 Well beneath the false bottom, an means for heatl g the Well, and a number of condensers vattached to the well, as and for the purpose specified.

HEI RIGH'F. D. SOHWAHN- Witnesses! 4 MAX DORN,

' N. A..DAvIs. 

